Lanark, IL Weather & Growing Conditions
Today
85°F
Partly Sunny then Slight Chance Showers And Thunderstorms
A slight chance of showers and thunderstorms after 5pm. Partly sunny. High near 85, with temperatures falling to around 83 in the afternoon. Southwest wind around 10 mph. Chance of precipitation is 20%.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 85°F | Partly Sunny then Slight Chance Showers And Thunderstorms | 10 mph SW | 16% |
| Tonight | 66°F | Showers And Thunderstorms Likely | 0 to 5 mph NW | 90% |
| Wednesday | 75°F | Showers And Thunderstorms then Showers And Thunderstorms Likely | 5 mph W | 78% |
| Wednesday Night | 60°F | Showers And Thunderstorms Likely | 0 to 5 mph N | 69% |
| Thursday | 78°F | Chance Rain Showers then Mostly Sunny | 0 to 5 mph NE | 32% |
| Thursday Night | 59°F | Mostly Clear | 0 mph | 7% |
| Friday | 80°F | Mostly Sunny | 0 to 5 mph SE | 4% |
| Friday Night | 63°F | Mostly Clear | 0 to 5 mph S | 8% |
| Saturday | 83°F | Mostly Sunny | 5 to 10 mph S | 11% |
| Saturday Night | 69°F | Partly Cloudy then Slight Chance Showers And Thunderstorms | 5 to 10 mph S | 21% |
| Sunday | 85°F | Slight Chance Showers And Thunderstorms | 10 to 15 mph SW | 21% |
| Sunday Night | 68°F | Chance Showers And Thunderstorms | 5 to 10 mph S | 41% |
| Monday | 84°F | Chance Showers And Thunderstorms | 5 to 10 mph S | 38% |
| Monday Night | 68°F | Slight Chance Showers And Thunderstorms then Chance Showers And Thunderstorms | 5 to 15 mph NW | 42% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Lanark, IL
Last spring frost
May 2
First fall frost
Oct 7
Growing season
154 days
Hardiness zone
5a
Explore more for Lanark, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Mt Carroll, Il (8.8 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.